High reactance transformer



HIGH REACTANOE TRANSFORMER Filed Dec. 28, 1962 2 Sheets-Sheet 1 INVENTOR: CLHRENCE 6. Dun/K6,

HTTOEA/EYS Aug. 31, 1965 Filed Dec. 28, 1962 C. G. DUENKE HIGH REACTANGETRANSFORMER 2 Sheets-Sheet 2 BVW /Is l EA/7' CLARE h/CE 6. DUENKE,

ATTOQNEY United States. Patent vOffice 3,204,210 Patented Aug. 31, 19653,204,210 HIGH REACTANCE TRANSFORMER Clarence G. Duenke, St. Louis, Mo.,assignor to Core Manufacturing Company, Washington, Mo., 21 corporationof Missouri Filed Dec. 28, 1962, Ser. No. 248,067 3 Claims. (Cl.336-165) This invention relates to a high reactance inductive device andparticularly to a high reactance transformer having the properties of aninitial high voltage output followed by an output at a controlledcurrent level. This kind of transformer is especially useful to startand then operate gas filled lamps such as mercury vapor lamps.

A characteristic of a gas filled lamp is that it requires a relativelyhigh starting or igniting voltage, but immediately after it is started,continued and normal operation of the lamp requires a limited currentflow. In general, these characteristics of gas filled lamps existbecause the initial ionization of the gas requires a high voltage, butafter ignition, as current flows through the lamp, the lamp impedancedecreases. Therefore, unless the operating voltage across the lamp isreduced, the current flow through the lamp will increase substantiallyand ultimately destroy the lamp or its circuit.

The general object of this invention is to provide a transformerforstarting and operating a gas filled lamp with a high leakagereactance for providing a high starting voltage followed by a controlledcurrent flow through the output of the transformer and through the lamp.

A specific object of the invention is to provide a transformer core thatmay be used with ahigh leakage reactance transformer wherein theconstruction of ,the core is such that when properly wound itprovides aflux path of high permeability linking the primary and. secondarywindings and a shunt havinga high leakage reactance connected across themain core between the primary and secondary windings. r

Another object of the invention is to provide a core structure for ahigh leakage reactance transformer that is extremely quiet in operation.

Another object of the invention is to provide a core for a high leakagereactance transformer that has a minimum copper loss.

Still another object of the invention is to provide a core for a highleakage reactance transformer that can be assembled quickly and easily.

Other objects and advantages will be apparent to those skilled in theart.

In the drawings:

FIGURE 1 is an isometric view of the core; and

FIGURE 2 is an isometric view of a transformer employing the core ofFIGURE 1.

Referring to FIGURE 1, the core comprises an outside loop 11 and aninside loop 12. The outside loop 11 is intended to provide a path formagnetic flux linking primary and secondary windings whereas the insideloop 12 provides a shunt.

The outside core loop 11 comprises a plurality of groups of magneticallyoriented metal strip laminations. In the core illustration there are twosuch lamination groups 13 and 14, the group 13 comprising one pluralityof laminations and the group 14 another plurality of laminations 16.Each of these laminations in the groups 13 and 14 makes a single turnabout the loop 11.

The laminations 15 of the group 13 have butt joints 17 that arestaggered in substantially a straight line along a leg of the loop 11,as clearly illustrated in FIGURE 1. The laminations of the group 14 alsohave staggered butt joints 18. As shown in FIGURE 1, the joints 17 and18 which are nearest one another are spaced apart a substantialdistance. Also, there is a single lamination 19 between the groups 13and 14 and having a butt joint 20 displaced a considerable distance fromthe joints 17 and 18. This lamination 19 acts as a locking laminationand also as a path for any flux bypassing the adjacent joints 17 and 18.

There are also locking laminations 21 and 22 on the outer and innersides of the core loop 11. These laminations 21 and 22 have single buttjoints 23 and 24 positioned at points spaced a substantial distance fromthe joints 17 and 18.

The outer loop 11 may comprise more than two lamination groups 13 and14, but it is preferable to include one or more locking laminations likethe lamination 19 between each group. In any event, the joints of each'material 32, but is otherwise disposed with its legs 28 and 29 next tothe legs 25 and 26 of the outer loop 11. Thus, the strip 32 introduces areluctance to the flow of flux from the core loop 11 to the loop 12.

All of the laminations 27 have cuts 34 to provide a single air gap onthe yoke 31. Therefore, the inner core loop 12 has a high reluctance tothe flow of flux. This is in contrast to the extremely low reluctanceand high permeability of the outer loop 11.

The core 10 may be used with a transformer 35 wound with a primary coil36 and a secondary coil 37 as illus- Itrated in FIGURE 2. The primarycoil 36 is wound around the adjacent legs 25 and 28 of both core loops111 and 12. The secondary coil 37 is wound only about a leg 25 of thelow reluctance outer core loop 11. The relative number of turns of theprimary and secondary coils may be chosen according to the desired inputand output characteristics of the transformer.

In operation, the primary winding 36 is connected across an alternatingcurrent power supply such as a standard volt 60 cycle supply. A gasfilled lamp, such as a mercury vapor lamp is connected across thesecondary coil 37. Such a lamp requires a high starting voltage.

With no current flow through the lamp, the flux induced by the currentflow through the primary coil 36 seeks the easiest path which is the lowreactance path through the outer core loop 11. Since this loop links theprimary and secondary coils 36 and 37, the magnetic flux links thesecoils and the maximum voltage occurs across the output conductors of thesecondary coil 37. As soon as the lamp ignites, it conducts and inducesa counter in the secondary coil 37 producing a reluctance to the flow offlux in the outer core loop 11. This increased reluctance causes theflux to bridge the air gap 34 in the shunt or yoke 31 of the inner coreloop '12 thereby reducing the flux in the outer core loop 11. Reductionof flux in the outer core loop of course reduces the voltage in thesecondary coil 37, and the current flowing through the coil, with acorresponding reduction in the counter Ultimately, the reluctance in theinner and outer core loops stabilizes and a stable current flow throughthe secondary coil 37 occurs. Under normal running conditions, the fluxflow in the outer and inner core loops 11 and 12 is about equal. Theextremely effective control produced by this transformer occurs becausethe outer core loop 11 has such a low reluctance whereas the inner coreloop 12 has a high reluctance produced by the air gap 34.

The assembly of this core is quick and easy. The lamination groups 13and 14 can be assembled together, thereby eliminating the tediousassembly of one lamination at a time. The inner core loop 12 should beassembled first by stacking the concentric laminations 27.

Assembly of the outer loop 11 begins with the inner locking lamination22 which is positioned about an appropriately sized arbor. Then thelaminations '16 comprising the group 14 are assembled together about theinner locking lamination 22, the joints 18 falling in place in the steprelationship illustrated. Next, the intermediate locking lamination 19is fixed in place, followed by the group 13 of the laminations 15.Finally the outer locking lamination 21 is fitted in place.

The two coils may be connected as either a two winding transformer or asan autotransformer. If the two coils are connected as anautotransformer, the gas filled lamp is connected across both theprimary coil 36 and the secondary coil 37. The primary coil 36 wouldbecome the common coil and the secondary coil 37 would become the seriescoil.

Various changes and modifications may be made within the purview of thisinvention as will be readily apparent to those skilled in the art. Suchchanges and modifications are within the scope and teaching of thisinvention as defined by the claims appended thereto.

What is claimed is:

1. A high reactance transformer comprising two core loops including aninner and an outer core loop each comprising a plurality of concentricmetal strip laminations, the inner core loop being positioned within theouter core loop and having a yoke extending between opposite legs of theouter core loop with an air gap thereacross, the laminations of theouter core loop comprising a plurality of separate groups with thelaminations of each group having staggered butt joints, a primary coilwound about adjacent legs of the inner and outer core loops, and asecondary coil wound about a leg of the outer core loop only, a lockinglamination between each group of laminations on the outer core loop, andlocking laminations on the inner and outer sides of the outer core loop,the locking laminations having butt joints located a substantialdistance from the staggered joints of the lamination groups.

2. A core for a high reactance transformer comprising two core loopsincluding an inner and an outer core loop each comprising a plurality ofconcentric metal strip laminations, the inner core loop being positionedwithin the outer core loop and having a yoke extending between oppositelegs of the outer core loop with an air gap thereacross, the laminationsof the outer core loop comprising a plurality of separate groups withthe laminations of each group having staggered butt joints, a lockinglamination between each group of laminations on the outer core loop, andlocking laminations on the inner and outer sides of the outer core loop,the locking laminations having butt joints located a substantialdistance from the staggered joints of the lamination groups.

3. A core for a high reactance transformer comprising two core loopsincluding an inner and an outer core loop each comprising a plurality ofconcentric metal strip laminations, the inner core loop being positionedwithin the outer core loop and having a yoke extending between oppositelegs of the outer core loop with an air gap thereacross, the laminationsof the outer core loop comprising a plurality of separate groups withthe laminations of each group having staggered butt joints, a lockinglamination between each group of laminations on the outer core loop, andlocking laminations on the inner and outer sides of the outer core loop,the outer core loop being generally rectangular with the staggered buttjoints being located on one side of the rectangle, the lockinglaminations having butt joints located on different sides of therectangle from the side on which the staggered butt joints are located.

References Cited by the Examiner UNITED STATES PATENTS 2,318,095 5/43Putman 336-212 X. 2,408,212 9/46 Hondette .s 336-219 X. 2,702,936 '3/55Hurt 336-211 X. 2,792,556 5/57 Olgesbee 336-221 X. 2,908,880 10/59Steinm-ayer et al. 336-212 X. 3,107,415 10/63 Ellis 336-215 X. 3,132,4135/64 Stopps 336-217 X.

JOHN F. BURNS, Primary Examiner. DARRELL L. CLAY, Examiner.

2. A CORE FOR A HIGH REACTANCE TRANSFORMER COMPRISING TWO CORE LOOPSINCLUDING AN INNER AND AN OUTER CORE LOOP EACH COMPRISING A PLURALITY OFCONCENTRIC METAL STRIP LAMINATIONS, THE INNER CORE LOOP BEING POSITIONEDWITHIN THE OUTER CORE LOOP AND HAVING A YOKE EXTENDING BETWEEN OPPOSITELEGS OF THE OUTER CORE LOOP WITH AN AIR GAP THEREACROSS, THE LAMINATIONSOF THE OUTER CORE LOOP COMPRISING A PLURALITY OF SEPARATE GROUPS WITHTHE LAMINATIONS